1. Field of the Invention
This invention relates to windshield wiper assemblies, in general, and to an improved wiper yoke and method of making same, in particular.
2. Description of the Prior Art
In German AS No. 1,075,450, a yoke formed from a sheet metal strip for a wiper blade is provided with oblong slots which improve the aerodynamic behavior of the wiper assembly. One slot is positioned in the main yoke between the articulating point of the wiper arm and the articulating point of the clawed yoke. The width of the slot is a multiple of the thickness of the sheet metal strip and is less than the spacing between the lateral shanks or sidewalls of the yoke. The main yoke and the similarly formed clawed yoke when viewed in cross-section in the area of the slots have two angular profiles to provide sufficient stability. However, because of the narrow width of the slots, this yoke arrangement does not meet requirements for aerodynamic behavior at high driving speeds.
In French Pat. No. 2,050,605, a wiper blade assembly similar to that described above is shown wherein the web of one yoke has a central separating line. Flanges lateral to the separating line are bent downwards parallel to the sidewalls of the yoke such that in the area of the slots, the cross-sectional view shows two U-shaped profiles. This yoke is relatively stable, but the aerodynamic behavior is less than desirable, again because the width of the slots is narrow. Additionally, this yoke is not easily fabricated using conventional production fabrication techniques.
Yokes for wiper blades are known from German AS No. 1,480,094 and 1,243,545 and from French Pat. No. 1,448,400 which provide slots having a width corresponding to the spacing of the lateral shanks, but the yokes comprise several piece parts. None of these yokes are formed from a single sheet metal strip.
Enormous difficulties have been encountered in producing a yoke formed of a metal sheet strip having wider slots. Proper bending of the strip in the area of the slots to form the sidewalls has not priorly been achieved when the spacing between the rim of the slots and the bending line approximately corresponds to the thickness of the sheet metal.
Additionally, a very rough punching edge is created when the slots are punched. The rough punching edge increases the danger of injury.